A novel method for the preparation ofion-conductive thin films by electrochemical vapor deposition was developed, and oxygen sensors were prepared using this method. The results obtained are summarized as follows :i) Dense yttria-stabilized zirconia (YSZ) films were formed on surface-oxidized nickel plates and nickel oxide pellets using a chemical vapor deposition-electrochemical vapor deposition (CVD-EVD) method.ii) Dense YSZ films were formed on the surface-oxidized nickel wire (100 mum in diameter) by the above method, and hollow YSZ fibers, which is a promising material for oxygen permeation membrane, were prepared by removing the Ni and NiO layrs from the YSZ/Ni/NiO composite.iii) A YSZ thin film formed on a small Ni/NiO pellet by CVD-EVD method, and an oxygen sensor was prepared using this composite.The sensor had a sensitivity for oxygen partial pressure even at a low temperature of 500ﾟC.